Polymer solutions



July 23, 1945 A. o. ROGERS POLYMER SOLUTIONS Filed Nov. 4, 1944III/ENTOR. ym 6- 7 ATTORNEY Patented July 23, 1946 UNITED STATES PATENTOFFICE POLYMER SOLUTIONS Application November 4, 1944, Serial No.562,013

11 Claims. 1

This invention relates to a new composition oi' matter and shapedarticles produced therefrom. More particularly, this invention relatesto an organic solvent solution of polyacrylonitrile, i. e. polymerlzedacrylonitrlle or polymerized vinyl cyanide (CH =CHCN);, and copolymersand interpolymers of acrylonitrile in which at least 85% by weight ofthe polymer is acrylonitrile, and the production of shaped articles fromsaid organic solvent solution of said polymers of acrylonitrile.

Polyacrylonltrile, and copolymers and interpolymers of acrylonitrilewith other polymerizable substances, for example vinyl or acryliccompounds in which at least 85% by weight of the polymer isacrylonitrile have been known for some time and recognized as possessingdesirable physical and chemical properties including toughness andinsolubility in and insensitivity to common organic solvents such asmethyl or ethyl alcohol, acetone, ethyl ether, ethyl acetate,hydrocarbon solvents, chlorinated hydrocarbons and the like. Because oithese facts, numerous attempts have been made to form these polymericmaterials into yarns, illms and other shaped articles.

The copending application of George H. Latham Serial No. 562,012, iledof even date herewith discloses solutions of polyacrylonltrlle indimethyl carbamyl compounds and the production of extruded and otherwiseshaped articles and structures from such solutions. The abovesaidapplication of George H. Latham represents the ilrst successfuldissolution of polyacrylonitrile in a solvent to produce a solutionwhich is suitable for the production of commercially useful textileyarns or wrapping tissue iilms, and similar tough, flexible structures.

The present application relates to a similarly satisfactory dissolutionof polyacrylonitrile in an organic solvent taken from a diierent classof organic compounds and the poiyacrylonitrile solutions producedthereby are similarly satisfactory for the production of tough,iiexible, dense, colorless yarns and films which are suitable for use inpractically al1 general commercial applications of such products.

It has been known heretofore that concentrated aqueous solutions ofinorganic salts such as lithium bromide, zinc chloride and sodiumsulfocyanide will dissolve polyacrylonitrile and it has been proposed(Rein U. S. Patent No. 2,140,- 921) to employ the resulting solutions inthe formation of yarns and films. However, it has been roundsubstantially impossible to use the (Cl. 26o-32) resulting compositionsin such a manner. Their extrusion into coagulating baths of the typeproposed (including such non-solvents for acrylonitrile as water, diluteacid, dilute salt solutions, etc.) result in the formation oi shapedarticles that contain large amounts of the inorganic salt of theproposed solvent. These salts are distributed throughout the structureand destroy the continuity of the polyacrylonitrile phase and l thestructure possesses poor physical properties.

l over, when lt is attempted to form a multifilament yarn by extruding.for examplefthe proposed aqueous sodium sulfocyanide polyacrylanitrilecomposition, into a dilute acid bath, it is found that the individualfilaments obtained stick together to form an essentially monolamentstructure that is extremely brittle and cannot be bent or worked withoutbreaking.

U. S. Patent No. 2,167,537 to Tobls points out that certain copolymersof acrylonltrile and an acrylic acid ester (those copolymers containingnot more than 65% of acrylonitrile) are soluble in mixtures of organicsolvents such as dioxan. monochlorbenzene, cyclohexanone. etc. However,these liquids are incapable o! dissolving or 30 even swellingpolyacrylonitriie or copolymers ot acrylonitrile containing higherpercentages of acrylonitrile, i. e. acrylonitrile polymers of the typewith which this invention is concerned. As previously mentioned,polymers containing such high percentages (at least 85% by weight) ofacrylonltrlle are especially desirable for use because of their goodphysical properties and excellent chemical resistance.

It has also been proposed (Rein U. S. Patent to dissolvepolyacrylonitrile in molten Quaternary ammonium salts such as benzylpyridinium chloride, an ionizable salt. Although the resulting solutioncan allegedly be used to form yarns or illxns of polyacrylonitrile,

the solution itself is dark red to brown ln color,

indicating that some decomposition of the polyacrylonitriie or somereaction between the polyacrylonltrile and the molten salt has probablytaken place. Such solutions are not satisfactory for the production ofcommercially useful, shaped are extremely brittle; they are highlycolored and very weak, presumably because of the presence within them ofresidual quaternary ammonium salt. Removal of this salt is difficult andthe resulting structures contain numerous and large voids that make thestructures .substantlalli7 useless for commercial purposes.

It is therefore an object of this invention to dissolvepolyacrylonitrile or a copolymer or interpolymer of acrylonitrile inwhich at least 85% by weight of the polymer is acrylonitrile, in asolvent which does not react with or decompose the polymer and which maybe substantially completely removed from the structures formed of such asolution.

It is another object of this invention to produce a solution ofpolyacrylonitrile or a copolymer or interpolymer of acrylonitrile inwhich at least 85% by weight of the polymer is acrylonitrilain a,solvent which ooes not react with or decompose the polymer, the solutionbeing suitable for the formation of commercially useful, void freearticles of polyacrylcnitrile, for example yarns which are suitable astextile yarns and films which are suitable as wrapping tissue.

It is another object of this invention to produce a solution ofpolyacrylonitrile, or a copolymer or interpolymer of acrylonitrile inwhich at least 35% by weight of the polymer is acrylonitrile. in avolatile organic solvent, which solution is stable over extended periodsof time and is eminently suited for use in the manufacture o! shapedarticles such as yarns, films, tubes, straws, artificial horsehair,bristles and ribbons, or when highly concentrated, for use in themanufacture of molded articles.

It is a still further object of this invention to produce shapedarticles and structures of polyacrylonitrile, or copolymers orinterpolymers of acrylonitrile in which at least 85% by weight of thepolymer is acrylonitrile.

It is stili another object of this invention to produce a shaped articleor structure of polyacrylonitrile or copolymers or interpolymers ofacrylonitrile in which at least 85% by Weight of the polymer isacrylonitrile, for example a yarn, lrn, tube, bristle or the like whichis tough, flexible, tenacious and free from voids.

Other objects of the invention will appear hereinafter.

The objects of the invention may be accomplished in general bydissolving polyacrylonitrile, or a copolymer or interpoiymer ofacrylonitrile in which at least 85% by weight of the polymer isacrylonitrile in an organic compound containing at least twocyanomethylene CHCN) groups and which is not a salt.

If the solvent has a relatively low boiling point (less than about 250C.), the solution of polyacrylonitrile may then be formed into a, shapedstructure, for example a yarn or film and the solvent removed from theshaped structure. When the solvent is relatively non-volatile and has aboiling point of about 300 C. or more, shaped articles may be made fromthe solution and at least a portion of the solvent may be retainedtherein as a. plasticizer for the articles.

It has been recognized in recent years that under certain conditions, anatom of hydrogen is attracted by rather strong forces to two atomsinstead of only one so that it may be considered to be acting as a bondbetween them. This is called the hydrogen bond.

The diiculty of dissolving polymers containing at least 85% by weightoi' acrylonitrile is due to the presence within the molecules of stronghy- CII 4 Y drogen-bonding forces and in order to dissolve one of thesepolymers, it is necessary to find a material which will undergo hydrogenbonding with the active hydrogen-bonding groups of the polymer moleculesand thus weaken the strong hydrogen bond within the `polymer moleculesand cause the hydrogen-bonding forces to be shared between molecules ofthe polymer and the solvent. In this manner, it is possible to i'orm amolecular dispersion of the polymer within the solvent and thus form asolution.

However, the strength of the hydrogen-bondlng capacity cannot be takenas the sole criterion as to whether or not a compound will function todissolve an acrylonitrile polymer. It is also necessary that, in orderto function as a solvent for an acrylonitrile polymer, the compoundcontain certain groups which will be capable of satisfactorily sharinga. hydrogen bonding force with the particular active group of theacrylonitrile polymer. In most instances, these groups require thepresence of a hydrogen atom on a carbon atom to which the group isattached (designated as an alpha-hydrogen atom). Such groups as requirethe alpha-hydrogen atom are ineffective to impart solvent power if thealpha-hydrogen atom is missing.

It has now been found that groups capable of conferring solvent powerinclude dimethyl carbamyl formyl mido cyano (--CENl sulfoxy groups,provided however that the cyano, thiocyano and sulfoxy groups requireattachment (through their respective unsatisfied carbon and sulfurvalences) to a carbon atom which is in turn attached to at least onehydrogen atom (alpha-hydrogen) in order to render them effective. Thedimethyl carbamyl and the formyl imido groups are effective in theabsence of the alpha-hydrogen atom. (It is possible that they containthe equivalent of an alpha-hydrogen thiocyano (-S-CEN) and atom withintheir own structures.) Thus, the groups dimethyl Carbamyl CH3 O I: l! il/N-o- CBI formyl imido (HCON cyanomethylene order named to form thesolvogenic group. the lower ranking group or groups present assumingmerely the nature of an inert substituent on the carbon atom.

It has furthermore been found that compounds containing theabove-mentioned soivogenic groups will be solvents for theabove-mentioned polymers only if the carbon content of the compound bewithin certain limits as given below. If the ratio of carbon tosolvosenic groupings is' maintained within the said limits, thecompounds will retain solvent properties of the polymer even though themolecule be of considerable size and complexity. The solvent power ofthe compound for acrylonitrile polymers is increased if additionalsolvogenic groups are present in the molecular structure of thecompound. the eiect of these groups being additive,

It has now been found that compounds which are fusible withoutdecomposition, containing at least two cyanomethylene groups andparticulariy those cyanomethylene compounds embraced by the followingempirical formula and preferably having a melting point below 250 C.will dissolve polyacrylonitrile, and copolymers and interpolymers ofacrylonitrile in which at least 85% by weight of the polymer isacryionitrlle:

0.()-CEN).

wherein q is an integer equal to or greater than 2; p is an integerequal to or greater than zero and of such a value that the ratio p/q isequal to or less than 1.5.

These compounds are not salts but may be cyclic or acyclic in nature andmay possess one or more ethylenic or acetylenig linkages. Valences otherthan those contained in carbon-to-carbon linkages and not shown assatisfied by the above formula must be satised by hydrogen, oxygen,bivalent sulfur, halogen, hydroxyl, thiol, cyano or thiocyano or sulfoxygroups, the total number of halogen, oxygen, sulfur, hydroxyl and thiolsubstituents not exceeding one half the value of q and the total numberof such cyano, thiocyano and sulfoxy substituents not exceeding thevalue of q. The two respective tolerances of one half q and of q, forthe said two groups of substituents are independent of each other andmembers of both groups may be present in the molecule up to their grouptolerances. The oxygen or sulfur atoms may appear in the compound asbivalent groups either as a side group (carbonyl or thiocarbonyl) orwithin the chain (ether or thioether) as the case may be.

Representative compounds coming within the scope of the above formulaand suitable for use as solvents for the above-mentioned acrylonitrilepolymers include:

CHI

NC-HCHaCN Methyl suceinonitrile CHCN News@ HON 1.2.3tricyanocyclopropane NC-CHsCHCHsCN 1,2,3 tricyanopropano C N NCCHsCHr-O-CHCHI Aipha,beta'dicyano diethyl other NCCBCHOHCHICNBeta-hydroxy giutal'onltrilo B(O HIONM This dlglycolionltrillNC-OHsCHxCHICN Glutaronitriie 0H NC-HC HnCN Malonitriia CHICHCHC Nl,l.2tricysncpropnm C E C El NC-CHC CN Alphabets-dimethylsuccinonitriloCIHI N C-CHCHsC N Alp ha-ethyisuccinonitrile C Hl C H C N Hi E CNi.2dicyanocyclobu tane C E. C HON N C-C H- Hl 1,3-dicyanocyclobutane NCCHCH CN NC E BCN l ,2.3.44etracyanccyciobutane C HIC H CHC N Hs H C Nl,2-dioyano3methyicyclobu tane NCCH|C H=C HCN Glutaoononitrile OH NC-OHxC HiHCN Aipha-hydmxyglu taronitriie ORC Ha N 0-013 H (IJH CNBetafmethylmalonitrilo C N 0 H N C-CHsC HzCHxC H-iJJ H C Nl,2,5tricyano-l-iiydroxypentane (N C C Hs) s 0 D igiycolionitrile [(NC-CH|)|C Hh() Bis-(bcta, beta' dicyanoisopropyl) ether N C C H: C Hl C NBuccinonitrlle NC-C HICHsCHiC Hs CN Adiponitrile (NC)|C (CHICBsCN):l,3,3,5tetncyanopentane N C C H H CN Fumaronitrile 0 (CHICHrCN) iBis(betseyanoethyl) ether S(CH:CH|CN) Bis(bctaoyanoethyl) sulfideAcrylonitrile polymer solutions formed by the use o! solvents embracedby the formula set forth above are stable at room temperature approxi-15 mately 20 C.) and at temperatures considerably above roomtemperature. Shaped structures and articles can be produced by extrudingmany of such solutions into an evaporative or coagulative medium. Byforming the structures in an evaporative medium. the solvent must beevaporated therefrom and by forming the structures in a coagulativemedium, the solvent should be removed by selective solution in anon-solvent for the polymer.

The solutions are prepared by dissolving the polyacrylonltrile, orcopolymer or intel-polymer oi acrylonitrile with one or a mixture oi'the above-mentioned solvents. Some oi these solvents are solid atordinary temperatures and dissolve or retain the polymer in clearsolution only at elevated temperatures. for example at temperatures ci100 C. or higher. below which temperature the composition resembles agel. In all cases when the polymer is dissolved in a solvent o! theabove class. the resulting composition while hot has the appearance of atrue solution. When cooled to room temperature, the compositiongenerally takes on the appearance of a gel, which gel may, on standing.undergo syneresis. Reheating or this gel or syneresed mass howevercauses it to again return to solution form.

In view of the relatively high melting points of some of the solvents ofthis invention, they would have comparatively little use in theproduction o! a polyacrylonitrile spinning or casting solution. Suchsolvents are, however, excellent solvent plasticizers forpolyacrylonitrile since they are soluble in a wide range of proportionswith the said acrylonitrile polymers. The present invention thereforecontemplates solid solutions of acrylonitrile polymers containing atleast 85% by weight of acrylonitriie as well as liquid solutionsthereof.

Shaped articles obtained from solvent solutions of polyacrylonitrile inaccordance with the invention and from which the solvent is subsequentlyremoved are substantially free of foreign matter and voids andsubstantially undecomposed and chemically unchanged from the simplepolymer prior to its solution.

The above-described organic solvent solutions of acrylonitrile polymermay be shaped in the i'orm oi' iilaments, yarns, films, tubes and likestructures by apparatus and processes generally known in the art, thedetailed operating conditions being suitably modified.

Suitable methods and apparatus for the production of shaped articles i'the polymers of this invention will be readily apparent by reference tothe following detailed description when taken in connection with theaccompanying illustrations in which:

Figure l is a diagrammatic vertical sectional view showing a dryspinning cell suitable for use in accordance with the invention;

Figure 2 is a diagrammatic perspective view showing a yarn drawingdevice for use in connection with the invention;

Figure 3 is a diagrammatic perspective view showing a wet spinningapparatus for use in the invention; and

Figure 4 is a diagrammatic side elevational view showing a suitable filmcasting apparatus for use in accordance with the invention.

Referring to Figure l of the drawing, reference numeral I I designatesa. spinneret through which a plurality of laments I5 are formed byextruding a filament-forming solution supplied to the spinner-et bymeans of conduit I3, The spinning cell is jacketed with a. material I1such as a reiractory in which is embedded an electrical heating coil I0.The spinning cell can thus be operated at any desired temperature. Aplurality of conduits 2| are provided adjacent the bottom of the devicefor passing evaporative medium through the cell so as to evaporate thesolvent from the extruded filaments I5. The evaporative medium isremoved from the cell through outlet openings 23. The yarn comprisingthe plurality of filaments I5 is passed from the bottom o! the spinningcell around guide roller 2l and is wound on a bobbin 21.

Referring to Figure 2 of the drawing, the yarn I5 is removed from thebobbin package 21 and passed about draw roller 29 and separating roller3 I. From draw roller 28, the yarn is passed to a second draw roller 33and separating roller 35. The yarn is passed around the two sets of drawrollers including their separating rollers a sumcient number of turns toprevent slippage of the yarn. Draw roller 33 is rotated at a greaterspeed, for example three to ten times the speed of draw roller 28. Inthis manner, the yarn Il is stretched between the two draw rollers. e Asthe yarn passes between the two draw rollers, a heating medium isbrought into contact with the yarn through blower nozzles 31 and 39. Theyarn passing from the draw roller 33 is wound on bobbin 4I. The drawingor stretching of the spun yarn as described is not claimed as part oi'the present invention, but is claimed in the copendins application ofDaniel T. Meloon, Serial Nc 496.397, filed July 28, 1943.

Figure 3 of the drawing illustrates a wet spin ning apparatus for theproduction of yarn. Thr acrylonitrile polymer solution is passed througlconduit 5I and is extruded through spinneret 53 to form a multifllamentyarn 5l. The yarn 5l is passed about guide roller 51 which is positionedwithin the coagulating liquid in tank 55. The yarn is then passed aboutguide roller 59 and is wound on bobbin Si. The organic solvent solutionof polyacrylonitrile may be cast in the form of a rllm as illustrated inFigure 4. In accordance with this apparatus, the polymer solution ispassed from hopper 1| on to the endless steel band 13 where it issmoothed by means of a doctor knife 15. The band. together with the nlm,is passed under a means 11 for bringing a heated drying medium intocontact with the film. The film 8| is pulled from the band 13 andcollected on a mill roll 83.

The polyacrylonitrile for use with the invention is preferably preparedby the ammonium persulfate catalyzed polymerization o! monomericacrylonitrile dissolved or emulsifed in water. It can, however, beprepared by any other suitable type oi' polymerization reaction such as,ior example. the emulsion type reaction disclosed by U. S. Patent No2,160,054 to Bauer et al. The polymer preferably possesses a molecularweight within the range oi' 15,000 to 250,000 or even higher, ascalculated from viscosity measurements by the Staudinger equation:

Molecular weight= Il;

viscosity of solution viscosity of solvent l The molecular weight of thepolymer obtained is dependent on auch factors as the concentration ofthe monomer in the water, the amount and type of catalyst present, thetemperature of the reaction, etc. For example, polyacrylonitrile, havinga molecular weight of approximately 60,000 can be prepared as follows:To 94 pounds of distilled water heated to 40 C. add 40 grams of ammoniumpersulfate catalyst and 80 grams of sodium bisulte activator. Then add16 pounds of acrylonitrile slowly with stirring over a period of twohours. The polyacrylonitrile having the above said molecular weight willprecipitate from the solution, Increasing or decreasing the amount ofthe catalyst, while maintaining the other conditions constant, decreasesor increases the molecular weight of the polymer. Acrylonitrilecopolymers and interpolymers containing at least 85% by weight ofacrylonitrile and likewise preferably having a molecular weight of15,000 to 250,000 or higher can be prepared in a similar manner.

The following examples in which parts, proportions and percentages areby weight unless otherwise specified illustrate preferred methods ofpreparing solutions oi' polymers in accordance with the principles ofthis invention and of employing these solutions in the manufacture ofcommercially satisfactory shaped articles of the polymer. the detailsset forth in the examples.

El'amlple I Fifteen (15) parts of an acrylonitrile polymer prepared bythe polymerization of monomeric acrylonitrile in accordance with thedisclosure of U. S. Patent No. 2,160,054 to Bauer et al. and possessingan average molecular weight of 120,000 as determined by the Staudingerequation on viscosity data are ground to an average particle size of 200mesh and mixed with 85 parts of glutaronitrile. This mixture is thenheated over a period of fifteen minutes to a temperature of 150 C. toform a clear solution. The solution was cast at a temperature of 170 C.on to a. polished, metallic surface heated to a temperature of 170 C. toform a thin, transparent lm of acrylonitrile polymer, the film beingtough, iiexible and tear resistant.

Example II Fifty (50) parts of a. copolymer prepared by the aqueousemulsion polymerization of 85 parts of acrylonitrile and parts ofisobutylene and possessing an average molecular weight of 66,000 asdetermined by viscosity data were mixed with 50 parts of1,3,3,5tetracyanopentane and heated over a period of thirty minutes to atemperature of 140 C. to form a clear, homogeneous dispersion orsolution. On cooling to room temperature, the composition set to aclear, rubbery solid that showed no sign of separating into itscomponent parts on prolonged standing, Similar results were obtainedwhen the copolymer of this example was replaced by one prepared from 85parts of acrylonitrile and 15 parts of vinyl acetate, methyl acrylate ordiethyl fumarate.

Example III Fifty (50) parts of the acrylonitrile polymer of Example IWere mixed with 50 parts of succinonltrile and heated to a temperatureof 150 C. to form a clear, homogeneous dispersion or solution which, oncooling, set to a, clear, viscous mass, At a temperature of 50 Cf, themass was rubbery in character. At lower temperatures, it became Theinvention is not to be limited by stiffer and harder, but showed notendency to separate into its component parte. In a second experiment,wherein 15 parts of this polymer were heated with 85 parts ofsuccinonitriie to form a clear dispersion or solution, the solid massobtained by cooling to room temperature was waxy in appearance. Hereagain, the composition ap peared to be stable and did not separate outon standing.

As indicated in the above examples, it is possible by the practice ofthis invention to obtain a solution of polyacrylonitrile, or a copolymeror interpolymer of acrylonitrile which is eminently suited for use inthe manufacture of shaped articles such as yarns, lms, or moldedarticles. These solutions are also suited for use as lacquers or coatingcompositions. They are especially useful in the coating oi' wire andelectrical parts where the high chemical and electrical resistance ofthe polymer is important.

For the purpose of deiinition, a solvent is a material which, when inthe'liquid state, is capable of forming solutions in which the polymeris present in a concentration by weight of 5% or more. In mostinstances, the polymer is soluble in almost all proportions although themiscibility may take place at elevated temperatures in the case ofcertain compounds.

As also shown, the solvents of the invention are useful not only inconnection with polyacrylonitrile, but also with copolymers andinterpolymers of acrylonitrile and with other polymerizable substancessuch as, for example, compounds containing one or more ethyleniclinkages including vinyl and acrylic compounds as well as oleflnic ordioleflnic hydrocarbons such as isobutylene, butadiene, etc. They areeminently satisfactory for use with those polymers that contain anappreciable amount of acrylonitrile, for example, polymers, copolymersand interpolymers that contain at least 85% by weight of acrylonitrileand that have generally been regarded by the art as being completelyinsoluble in all common organic solvents. Nor are these solvents limitedto use with a polyacrylonitrile of any given molecular weight. They canbe used with a polymer of almost any given molecular weight and areespecially satisfactory for use with those polymers having an averagemolecular weight within the range 15,000 to 250,000 as determined byviscosity data using the Staudinger equation and intended for use in themanufacture of yarns or films.

The solution of acrylonitrile polymer dissolved in an organic solvent inaccordance with this invention must be of such a concentration that itsviscosity at the operating temperature is within a workable range. Whenit is to be employed in the spinning of yam or the casting of film, the

solution should preferably have a viscosity within the range 25 to 750poises. When the polymer has a molecular weight of 250,000 or more, thisrequires that the maximum concentration of poylmer in the spinningsolution be of the order of 10%. Generally, it is preferred that thespinning solution contain at least 10% of the polymer because or thedifficulty of rapidly removing large amounts of solvent from thesolution in the spinning operation. Moreover, it is economicallyundesirable to use such large amounts of solvent for the spinning of agiven amount of polymer although it is true that the solvent can becornpletely recovered from the spinning operation and reused. For thesereasons, it is preferred to employ a polymer having an average molecularweight of between 40,000 and 150,000 since such a l l poylmer forms ssolution of the desired viscosity in concentrations of the order of 15%to 25% and at a desirable spinning temperature of the order o1' 100" to150 C. 0f course, itis within the scope of the invention to heat thesolution to a higher temperature, even to above the normal boiling pointof the solvent, for the actual spinning op. eration. Here again, thecontrolling factor with regard to the temperature of the spinning solu-A tion is the viscosity of the solution.

The evaporative medium employed in the dry spinning of filaments andyarns or the dry casting of films in accordance with this invention maybe any vapor inert to the iilmor filament-forming solution such as air,nitrogen, steam, etc., or any suitable mixture thereof. The temperatureof the evaporative medium is dependent on such factors as the dimensionsof the spinning cell, the composition and rate of extrusion of thespinning solution and the rate oi flow of the evaporative medium. It isonly necessary that these several factors be so correlated that the yarnor other shaped article leaving the spinning cell be suillciently freedof the solvent so that it is solidified and capable of being wound intopackage form or otherwise collected.

Shaped articles of acrylonitrile polymer can also be formed by extrudingthe spinning solution into a suitable precipitating bath comprising aliquid that is miscible with the solvent but is a chemically inertnon-solvent for the acryionitrile polymer. As examples of such a liquidmay be mentioned water, glycerin, organic solvents such asalcohol,ether. etc., or aqueous solutions of salts, alkalies or acids. Thecopending application of William W. Watkins, Serial No. 496,376, fliedJuly 28, 1943, covers the use o! glycerol and aqueous solutions of saltsas baths, preferably at elevated temperatures, for the wet spinning ofacrylonitrile polymer yarn, from solutions of the polymer, preferablywith substantial tension and stretch being applied during spinning.

The article of acrylonitrile polymer thus obtained can advantageously besubjected to a stretching operation or the type employed in the aboveexamples. This stretching is preferably performed by passing the yarnbetween two positively driven rollers, the peripheral speeds of whichare so adjusted that the article is stretched from two to ten times itsoriginal length, preferably approximately six times its original length.This stretching of the formed article may be performed at any suitabletime. However, in the case of articles formed by the wet spinning orcasting technique, it is preferably performed before the article hasbeen completely dried. The orientation of the structure thus obtainedimproves the physical properties of the structure including itstenacity, its resilience. etc.

This stretching of the shaped article can also be accomplished bycausing the article, while passing between stretching rollers, tocontact a heated stationary pin or to pass through an inert medium suchas air, water, glycerin, etc., heated to a high temperature. Obviously,the article must not be exposed t this high temperature for a periodsufficiently long to decompose the polymer. In general however, the timeof contact of the article with the heated medium is so short thattemperatures up to 250 C. can be employed. Although it is generallypreferred to heat the article to a temperature of at least 100 C. duringthe stretching operation, this is not essential. Desirable results canbe obtained by stretching the article without the application polymer.

12 oi heat, for example by stretching at room temperature.

In addition to acting as solvents for polyacrylonitrile, or copolymersof acrylonitrile, the aliphatic or arylaliphatic nitrile compounds ofthis invention, when present in small amounts, can also be used asplasticizing agents for the polymer and the higher boiling compounds ofthe invention are especially suited for use use. At the same time, itis, of course, to be understood that non-solvent soiteners, such asglycerol. can also be incorporated in the solutions of the invention,these materials remaining in the subsequently formed articles to imparta softening effect. If it is desired to use such plasticizing orsoftening agents with polyacrylonitrile. they are preferably added inthe desired amount to an already formed solution of the polymer in alower boiling solvent, for example to a solution of the polymer indimethyliormamide.

This invention is primarily concerned with the steps of dissolvingpolyacrylonitrile in a suitable solvent to form a. stable solutionadapted for use in the manufacture of shaped articles oi' poly.-acrylonitriie. It is characteristic of the invention that the solutionsprovided by it are stable: the solvents do not cause a decomposition orchemical alteration of the dissolved acrylonitrile At the same time, itis also characteristie that the solvents provided by the invention arealso useful in the dissolving of mixtures of polyacrylonitrile andadjuvants such as dye modiers, linear polyamides such as nylon.derivatives of cellulose including cellulose ethers and esters, polymersof vinyl compounds such as vinyl chloride, vinyl acetate, acrylic acid,etc., which adjuvants may be incorporated in the acrylonitrile polymersolution to modify the properties, both chemical and physical, of theresulting shaped articles.

This invention provides a class of solvents for polyacrylonitrile, andcopolymers and interpolymers of acrylonitrile which were heretoforeconsidered substantially insoluble. 'Ihe solvents are capable of formingwith the polymer clear solutions that are stable for extended periodsoi' time and are admirably suited for use as lacquers or coatingcompositions or in the manufacture of shaped articles of the polymer,for example by extrusion into an evaporative or coagulative medium, orby the use of a molding technique.

The invention also provides a class of materials that is eminentlysuited for use in plasticizing structures comprising the acrylonitrilepolymers. The materials provided by this invention are apparently truesolvents for the above-mentioned acrylonitrile polymers. They do nottend to react with or decompose the polymer, the polymeric materialobtained from the solution of this invention apparently being the sameidentical chemical composition as the initial polymer.

Yarns, films and similar articles oi' polyacrylonitrile prepared fromthe solutions of this invention can be stretched to yield orientedstructures that possess a high tenacity, a desirable elongation and ahigh elastic recovery that compares favorably with that of silk. Thearticles are not contaminated with undesirable salts and they aresubstantially free of void spaces,

Reference, throughout the specification and claims, to acrylonitrilepolymers, polymers of acryionitrile, and copolymers and interpolymers ofacrylonitrile containing at least by weight of acrylonitrile" signifiespolymers containing in their molecules at least 85% by weight 13 of theacrylonitrile unit which is considered to be present in the polymermolecule as the group that is, at least 85% by weight of the reactantmaterial converted into and forming the polymer is acrylonitrile.

Since it is obvious that many changes and modifications can be made inthe above described details without departing from the nature and spiritof the invention, it is to be understood that the invention is not to belimited to the details described herein except as set forth in theappended claims.

I claim:

1. As a new composition of matter, a polymer of acrylonitrile containingin the polymer molecule at least 85% by weight of acrylonitriledissolved in an organic nitrile compound embraced by the formula:

has.)

wherein q is an integer at least equal to 2; p is an integer at leastequal to zero such that the ratio p/q does not exceed 1.5; all valencesof said compound other than those contained in carbonto-carbon linkagesand not shown as satisfied in the formula being satisfied by asubstituent taken from the group consisting of hydrogen, halogen,oxygen, bivalent sulfur, thiol, hydroxyl, cyano, thiocyano and sulfoxy;the total number oi' halogen, oxygen, sulfur, hydroxyl and thiolsubstituents not exceeding one half the value of q and the total numberof cyano, thiocyano and sulfoxy groups not exceeding the value oi q.

2. A new composition of matter as defined in claim 1, in which thepolymer is polyacrylonitrile.

3. A new composition of matter as defined in claim 1, in which thepolymer has a molecular weight between 15,000 and 250,000.

4. A new composition of matter as deiined in 14 claim 1, in which thePolymer has a molecular weight between 40,000 and 150,000.

5. A new composition of matter as defined in claim 1, in which theviscosity of the polymer solution is within the range 25 to '750 poises,

6. As a new composition oi matter, a polymer of acrylonltrile containingin the polymer molecule at least 85% by weight of acrylonitriledissolved in succinonitrile.

7. As a new composition of matter, a polymer oi' acrylonitrilecontaining in the polymer molecule at least 85% by weight oiacrylonitrile and an organic nitrile compound embraced by the formula:

n Cham) wherein q is an integer at least equal to 2; p is an integer atleast equal to zero such that the ratio P/q does not exceed 1.5; allvalences oi' said compound other than those contained in carbonto-carbonlinkages and not shown as satised in the formula being satisfied by asubstituent taken from the group consisting of hydrogen, halogen.oxygen, bivalent sulfur, thiol, hydroxyl, cyano, thiocyano and sulfoxy;the total number of halogen, oxygen, sulfur, hydroxyl and thiolsubstituents not exceeding one half the value of q and the total numberoi cyano, thiocyano and suli'oxy groups not exceeding the value of q.

8. The composition of claim 1 in which the solution contains at least10% ci said polymer of acrylonitrile.

9. The composition or claim 1 in which the polymer is polyacrylonitrilehaving a molecular weight of between 15,000 and 250,000.

10. The composition oi' claim 1 in which the polymer ispolyacrylonltrile having a molecular weight of between 40,000 and150,000.

1l. The composition ci' claim 6 in which the polymer ispolyacrylonitrile.

ARTHUR 0. RCGERB.

Certiiicate of Correction Patent No. 2,404,715.

July 23, 1946.

ARTHUR O. ROGERS ilkewise read likeuse; column l2,

subscript after C at the beginningf It is hereby certified that errorsappear in the rnted numbered patent requiring correction as follows:

the formula read p; column 9, line 19, for

e 9, for use use read auch use; and that the secicaton of the above Coumn 5, ne 29, for the indistinct said Letters Patent should be read withthese corrections therein that the same may conform to the record of thecase in the Patent Oiiice.

Signed and sealed this 29th day of October, A. D. 1946.

LESLIE FRAZEB.

First Assistant Uanmtseoner of Patents.

13 of the acrylonitrile unit which is considered to be present in thepolymer molecule as the group that is, at least 85% by weight of thereactant material converted into and forming the polymer isacrylonitrile.

Since it is obvious that many changes and modifications can be made inthe above described details without departing from the nature and spiritof the invention, it is to be understood that the invention is not to belimited to the details described herein except as set forth in theappended claims.

I claim:

1. As a new composition of matter, a polymer of acrylonitrile containingin the polymer molecule at least 85% by weight of acrylonitriledissolved in an organic nitrile compound embraced by the formula:

has.)

wherein q is an integer at least equal to 2; p is an integer at leastequal to zero such that the ratio p/q does not exceed 1.5; all valencesof said compound other than those contained in carbonto-carbon linkagesand not shown as satisfied in the formula being satisfied by asubstituent taken from the group consisting of hydrogen, halogen,oxygen, bivalent sulfur, thiol, hydroxyl, cyano, thiocyano and sulfoxy;the total number oi' halogen, oxygen, sulfur, hydroxyl and thiolsubstituents not exceeding one half the value of q and the total numberof cyano, thiocyano and sulfoxy groups not exceeding the value oi q.

2. A new composition of matter as defined in claim 1, in which thepolymer is polyacrylonitrile.

3. A new composition of matter as defined in claim 1, in which thepolymer has a molecular weight between 15,000 and 250,000.

4. A new composition of matter as deiined in 14 claim 1, in which thePolymer has a molecular weight between 40,000 and 150,000.

5. A new composition of matter as defined in claim 1, in which theviscosity of the polymer solution is within the range 25 to '750 poises,

6. As a new composition oi matter, a polymer of acrylonltrile containingin the polymer molecule at least 85% by weight of acrylonitriledissolved in succinonitrile.

7. As a new composition of matter, a polymer oi' acrylonitrilecontaining in the polymer molecule at least 85% by weight oiacrylonitrile and an organic nitrile compound embraced by the formula:

n Cham) wherein q is an integer at least equal to 2; p is an integer atleast equal to zero such that the ratio P/q does not exceed 1.5; allvalences oi' said compound other than those contained in carbonto-carbonlinkages and not shown as satised in the formula being satisfied by asubstituent taken from the group consisting of hydrogen, halogen.oxygen, bivalent sulfur, thiol, hydroxyl, cyano, thiocyano and sulfoxy;the total number of halogen, oxygen, sulfur, hydroxyl and thiolsubstituents not exceeding one half the value of q and the total numberoi cyano, thiocyano and suli'oxy groups not exceeding the value of q.

8. The composition of claim 1 in which the solution contains at least10% ci said polymer of acrylonitrile.

9. The composition or claim 1 in which the polymer is polyacrylonitrilehaving a molecular weight of between 15,000 and 250,000.

10. The composition oi' claim 1 in which the polymer ispolyacrylonltrile having a molecular weight of between 40,000 and150,000.

1l. The composition ci' claim 6 in which the polymer ispolyacrylonitrile.

ARTHUR 0. RCGERB.

Certiiicate of Correction Patent No. 2,404,715.

July 23, 1946.

ARTHUR O. ROGERS ilkewise read likeuse; column l2,

subscript after C at the beginningf It is hereby certified that errorsappear in the rnted numbered patent requiring correction as follows:

the formula read p; column 9, line 19, for

e 9, for use use read auch use; and that the secicaton of the above Coumn 5, ne 29, for the indistinct said Letters Patent should be read withthese corrections therein that the same may conform to the record of thecase in the Patent Oiiice.

Signed and sealed this 29th day of October, A. D. 1946.

LESLIE FRAZEB.

First Assistant Uanmtseoner of Patents.

